JP2693041B2 - Application method of thermosetting adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a thermosetting adhesive, and more particularly to prevention of hardening of the adhesive accompanying application.

[0002]

2. Description of the Related Art Thermosetting adhesives are used for temporarily fixing electronic parts to printed circuit boards. At the time of application, the compressed gas supplied to the syringe and the applying step of applying the compressed gas into the syringe containing the thermosetting adhesive to discharge the adhesive from the nozzle in a predetermined amount each time and applying it to the object to be coated are performed. The exhaust process of discharging is repeated.
The execution of the evacuation process lowers the pressure inside the syringe to atmospheric pressure, and the discharge of the adhesive is stopped. The adhesive applied in this manner is cured by heating and adheres the adhesive to the object to be applied. However, when the adhesive is an adhesive weak to high temperature such as electronic parts, the curing temperature is low. Adhesive is used.

[0003]

However, when the curing temperature of the adhesive is low, a part of the adhesive may be cured in the syringe and the nozzle may be clogged, which may hinder the application. This is because the temperature of the syringe and the adhesive increases as the application is repeated. In the exhaust process, the gas in the syringe is discharged, but this discharge stops when the pressure in the syringe drops to atmospheric pressure, so a certain amount of gas remains in the syringe, and this residual gas is It is compressed in the syringe by the compressed gas supplied in the coating step. That is, since the compression and expansion of the gas are repeated in the syringe while the coating operation is being performed, the temperature of the compressed gas itself supplied to the syringe is high, and the temperature of the compressed gas itself is not high. However, as the temperature of the residual gas in the syringe gradually rises, heat is also accumulated in the syringe and the adhesive, and their temperatures rise to near the curing temperature of the adhesive. This problem becomes more important as an adhesive having a lower curing temperature is used and the number of adhesive application points per unit time increases.

It is an object of the present invention to provide a method capable of suppressing the temperature rise in the syringe to a low level and continuing to apply the adhesive without curing.

[0005]

In order to solve the above-mentioned problems, the coating method of the present invention comprises:
In addition to (b) the exhausting step, (c) a scavenging step for exhausting the gas remaining in the syringe by fresh air after the exhausting step is provided.

[0006]

When the scavenging step is executed after the evacuation step, the high temperature compressed gas remaining in the syringe is discharged, and the fresh air cools the syringe and the adhesive to suppress the temperature rise in the syringe. The exhaust process is a process in which the compressed gas supplied to the syringe is discharged to stop the discharge of the adhesive, and the scavenging process is a process in which the gas remaining in the syringe without being discharged is replaced with fresh air. And
The exhaust process and the scavenging process do not necessarily need to be distinctly performed.

[0007]

As described above, according to the coating method of the present invention, temperature rise in the syringe can be suppressed, and good coating can be performed without curing of the adhesive. If the number of adhesives applied per unit time is the same, it is possible to apply an adhesive with a low curing temperature, and if the curing temperature is the same, it is possible to increase the number of applications per unit time and improve work efficiency. It becomes.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings by taking an example of applying an adhesive to a printed circuit board.

FIG. 1 shows a coating head 10 used for carrying out a coating method according to an embodiment of the present invention.
The coating head 10 includes a syringe 12 and a coating nozzle 16 attached to a lower end of the syringe 12 via a cylindrical adapter 14.
And The coating nozzle 16 has an inner diameter of 0.6 mm.
One discharge pipe 18 is attached. Further, the syringe 12 has a bottomed cylindrical shape, accommodates an acrylic thermosetting adhesive 20, and a float 22 for detecting a residual amount is placed on the adhesive 20. The opening of the syringe 12 is airtightly closed by a lid 24, and a joint member 26 is airtightly fitted to the lid 24. A first air passage 28 and a second air passage 30 are formed in the joint member 26. One end of the first air passage 28 is opened to an air chamber 32 between the adhesive 20 in the syringe 12 and the lid body 24, and the other end is provided with a pipe 34 configured by a hose or the like to supply a compressed air supply for application. It is connected to 36. In the middle of the pipe 34, the electromagnetic directional control valve 3
8 is provided, and the air chamber 32 is
It can be switched between a state of communicating with the coating compressed air supply source 36 and a state of communicating with the atmosphere via the silencer 40.

Further, one end of the second air passage 30 has an air chamber 3
2, and the other end is connected to a scavenging compressed air supply source 48 by a pipe 46. An electromagnetic opening / closing valve 50 is provided in the middle of the pipe 46, and the air chamber 32 is switched between a state in which compressed air is supplied from the scavenging compressed air supply source 48 and a state in which compressed air is not supplied. It should be noted that the coating compressed air supply source 36 and the scavenging compressed air supply source 48 both adjust the compressed air supplied by the compressor for the factory to a required pressure by a regulator,
It is supplied to the syringe 12. The diameter of the portion of the pipe 46 between the electromagnetic on-off valve 50 and the second air passage 30 is 8 mm.

Next, the operation will be described. The coating head 10 is
By a moving device (not shown), the adhesive 2 is moved to the printed circuit board in the X direction and the vertical direction in the horizontal plane.
Apply 0. Further, in the present embodiment, the pressure of the compressed air supplied by the compressed air supply source for coating 36 is 2.5 kg /
cm ² , the pressure of compressed air supplied by the scavenging compressed air source 48 is 0.5 kg / cm ² , the amount of application is 5 g per time, the ambient temperature is 25 degrees, and the application is performed at a rate of 8 times per second. Then, 4000 points are applied on one printed circuit board.

At the time of non-coating, the solenoids of the electromagnetic directional control valve 38 and the electromagnetic on-off valve 50 are demagnetized, the compressed air supply source 48 for scavenging compressed air is supplied to the air chamber 32, and The air is exhausted through the air passage 28 and the silencer 40. Therefore, the air chamber 3
The pressure in 2 is almost atmospheric pressure. During coating, the solenoid of the electromagnetic directional control valve 38 is excited, the air chamber 32 is communicated with the coating compressed air supply source 36, and the electromagnetic opening / closing valve 50 is closed. As a result, relatively high pressure compressed air is supplied to the air chamber 32, and the air chamber 32
The pressure inside rises to nearly 2.5 kg / cm ² and floats 2
2 is pushed down, the adhesive 20 is discharged from the discharge pipe 18 and applied to the printed circuit board. The amount applied once is 5
The supply time of the compressed air required to discharge the gram of the adhesive 20 is set in advance, and when the supply time elapses, the solenoid of the electromagnetic directional control valve 38 is demagnetized, and the air chamber 32 is released.
Is opened to the atmosphere and the hot compressed air in the air chamber 32 is discharged from the silencer 40. This exhaust air chamber 3
When the pressure in 2 becomes almost equal to the atmospheric pressure, the electromagnetic on-off valve 50 is opened, and new compressed air is supplied from the compressed air supply source for scavenging 48 to replace the high temperature air remaining in the air chamber 32. At the same time, the syringe 12, the float 22, the adhesive 20, etc. are cooled by the compressed air of relatively low pressure and low temperature, and the temperature of the air chamber 32 is lowered. Therefore, when the adhesive 20 is applied, the temperature of the air chamber 32 rises due to the compression of the air in the air chamber 32, but the temperature rise of the adhesive 20 and the like is suppressed by the subsequent scavenging, and the curing of the adhesive 20 is prevented. It Compressed air for scavenging is the next adhesive 20
Can be continuously supplied until the application.

If the compressed air for application is supplied and the compressed air for scavenging is supplied to the air chamber 32 so that the compressed air is exhausted after the compressed air for supply is supplied as in the present embodiment, the scavenging air can be discharged. Air chamber 3 when compressed air is supplied for
Since the pressure in 2 is low, the high temperature compressed air does not flow back to the scavenging compressed air supply source 48 side, but is quickly discharged and the temperature rise of the syringe 12 is effectively suppressed.

In order to confirm the effect of the apparatus of this embodiment, an experiment was conducted in which a large number of adhesives were applied to a printed circuit board at intervals of 10 mm. The temperature change of the air chamber 32 at that time is shown in the graph of FIG. This temperature is set in the air chamber 32 on the peripheral wall of the syringe 12.
A thermocouple was provided at the portion corresponding to the above with its tip penetrating into the air chamber 32, and measurement was performed. As is clear from this graph, the temperature remains 4 even if the adhesive 20 is repeatedly applied.
It only rises to 0 degrees. For comparison, the temperature of the air chamber 32 during application of the conventional adhesive is shown in the graph of FIG. This coating is performed under the same conditions as the coating of the above example,
The temperature rose to 72 degrees. In the graph of FIG. 3, the portion where the temperature is lowered is the portion where the application is temporarily stopped while the application to the one row of adhesive application points is completed and the printed circuit board is retracted. As is clear from this measurement result, the temperature of the air chamber 32 rises due to the application of the adhesive, but the temperature rise is suppressed by the scavenging. Note that the compressed air for scavenging was supplied to the air chamber 32 even during non-application, but the adhesive 20 did not ooze out from the discharge pipe 18.

The effect of suppressing the temperature rise due to such scavenging can be obtained without causing bleeding of the adhesive 20 from the discharge pipe 18 when the pressure of the scavenging compressed air is low and the flow rate thereof is large. This is clear from the following three types of experimental results. The graph shown in FIG. 4 shows the temperature of the air chamber 32 when the pressure of the compressed air for scavenging is 5 kg / cm ² and the diameter of the pipe is 4 mm, which rises to 47 degrees, which is lower than the conventional temperature. The bleeding of the adhesive 20 from the discharge pipe 18 was observed. Further, the graph shown in FIG. 5 shows the temperature of the air chamber 32 when the pressure of the compressed air for scavenging is 1 kg / cm ² and the diameter of the pipe is 4 mm.
There was no bleeding of 0. Further, the graph shown in FIG. 6 shows the temperature of the air chamber 32 when the pressure of the compressed air for scavenging is 1 kg / cm ² and the diameter of the hose is 8 mm, which is 38 degrees, but the bleeding of the adhesive 20 is there were. From these facts, the temperature rise suppression effect depends on the flow rate rather than the pressure level of the scavenging compressed air, and the bleeding-out occurs if the pressure in the air chamber 32 is low (scavenging air It can be seen that the pressure in the air chamber 32 does not decrease if the diameter of the pipe for guiding the compressed air for use is small).

Another embodiment of the present invention is shown in FIG. In this embodiment, the supply of compressed air from the compressed air supply source 36 for coating and the compressed air supply source 48 for scavenging to the air chamber 32 is switched by one electromagnetic directional control valve 60. The electromagnetic directional control valve 60 is a 5 port / 2 position directional control valve, and the first air passage 28 is connected to the compressed air supply source 48 for scavenging.
And a second position where the second air passage 30 is opened to the atmosphere and a second position where the first air passage 28 is communicated with the coating compressed air supply source 36 and the second air passage 30 is closed. . The flow rate of the scavenging compressed air is reduced by the throttle 62.

In the present embodiment, the electromagnetic directional control valve 60 is at the first position during non-application, and the compressed air is supplied to the air chamber 32 even during the application to perform scavenging. During application, the electromagnetic directional control valve 60 is switched to the second position, compressed air is supplied from the compressed air supply source 36 for application for a predetermined time, and the adhesive 20 is applied. After application, the electromagnetic directional control valve 60 is switched to the first position, the hot compressed air in the air chamber 32 is discharged, and the air is scavenged. In the case of the present embodiment, after the application time has elapsed, the electromagnetic directional control valve 60 is switched to the first position, the compressed gas in the air chamber 32 is discharged through the silencer 40, and the air chamber 32 is compressed for scavenging. Although the air is supplied, the pressure of the compressed air is low, so that the high-pressure coating compressed air in the air chamber 32 initially flows back to the scavenging compressed air supply source 48 side, and then the compressed backflowing compression occurs. The air is pushed back by the compressed air for scavenging and discharged from the air chamber 32. The exhausting process is performed until the backflow of the air to the air chamber 32 is completed, and the scavenging process is performed while the high temperature air remaining in the air chamber 32 is replaced with fresh air.

Another embodiment of the present invention is shown in FIG. In this embodiment, the supply source of compressed air for applying the adhesive 20 and the supply source of compressed air for scavenging are made common. The compressed air supply source 64 includes a regulator 66,
It is connected to the first air passage 28 by a pipe provided with an electromagnetic direction switching valve 68, and is connected to the second air passage 30 by another pipe provided with a regulator 70, a check valve 71, and a throttle 72. . The control pressure of the regulator 66 is set higher than the control pressure of the regulator 70. When the adhesive is not applied, the electromagnetic directional control valve 68 is in the state shown in the figure, the low pressure compressed air controlled by the regulator 70 is supplied to the air chamber 32, and the first air passage 2
8. The electromagnetic directional control valve 68 is discharged to the atmosphere, the electromagnetic directional control valve 68 is switched to the state on the right in the drawing at the time of application, and high-pressure compressed air is supplied to the air chamber 32, so that the adhesive 20 is removed. Is ejected.

When only one source of compressed air is provided,
It can also be configured as shown in FIG. The first air passage 28 is connected to a compressed air supply source 76 by a pipe provided with a throttle 74, and the second air passage 30 is connected to the electromagnetic opening / closing valve 7.
By switching of 8, the state is opened to the atmosphere and the state is closed. The pressure of the compressed air supplied from the compressed air supply source 76 to the air chamber 32 is constant, but when the electromagnetic opening / closing valve 78 is opened, the compressed air supplied is because the air chamber 32 is in communication with the atmosphere. Pressure decreases, the pressure in the air chamber 32 does not rise, and the adhesive 20 is not discharged. If the electromagnetic on-off valve 78 is closed, the air chamber 32
When the internal pressure rises, the adhesive 20 is discharged, and then the electromagnetic opening / closing valve 78 is opened, the compressed air in the air chamber 32 is first exhausted and then scavenged.

Yet another embodiment of the present invention is shown in FIG.
In this embodiment, as in the embodiment of FIG.
The compressed air supplied to the air chamber 80 is discharged from the peripheral wall 84 of the syringe 82 while being provided individually. A hose connection port 88, an air chamber 90, and a plurality of air holes 92 are provided in the lid 86 that closes the opening of the syringe 82, and the compressed air supply source 9 is provided by a pipe 96 having a throttle 94.
8 is connected. Further, the float 100 is provided with an air chamber 102, a plurality of air holes 104 for communicating the air chamber 102 with the air chamber 80, and is connected to an opening 108 provided in the peripheral wall 84 by a hose 106. The opening 108 can be switched between a state in which it communicates with the atmosphere and a closed state by switching the electromagnetic opening / closing valve 110.

When the adhesive is not applied, the electromagnetic on-off valve 110 is opened, the pressure in the air chamber 80 does not rise, and the compressed air supplied by the compressed air supply source 98 is discharged through the hose 106. Since the electromagnetic opening / closing valve 110 is closed at the time of application, the pressure in the air chamber 80 rises and the float 10
0 is pushed down and the adhesive 20 is discharged. In the present embodiment, the compressed air for scavenging flows from one end of the air chamber 80 to the other end, so that the scavenging is performed reliably, and the compressed air for scavenging is arranged in the adhesive 20. Since it flows through the hose 106, there is an advantage that the adhesive 20 is cooled by the air flow.

In each of the above embodiments, the air at room temperature is compressed and supplied to the air layer as it is, but the compressed air may be cooled before supplied. Further, although air is used as the compressed gas in the above embodiment, a gas other than air may be used, such as supplying nitrogen from a nitrogen cylinder. When the compressed gas is supplied from the cylinder, the temperature of the compressed gas itself becomes lower than room temperature, so that the temperature rise of the syringe and the adhesive can be better avoided.

Furthermore, in each of the above-described embodiments, the case where the adhesive is applied by the application head 10 having one syringe 12 has been described, but it is also applicable to the adhesive application in which a plurality of syringes 12 are used alternately or simultaneously. The present invention can be applied. In addition, without departing from the scope of the claims, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an application head used in a method for applying a thermosetting adhesive which is an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the temperature of the air chamber of the syringe and the time when the adhesive is applied by the above application method.

FIG. 3 is a graph showing the relationship between the temperature of the air chamber of the syringe and time when the adhesive is applied by the conventional application method.

FIG. 4 is a graph showing a temperature change of an air chamber obtained in an experiment up to the coating method of the above-mentioned embodiment.

FIG. 5 is a graph showing a temperature change of an air chamber obtained in an experiment up to the coating method of the above-mentioned embodiment.

FIG. 6 is a graph showing a temperature change of an air chamber obtained in an experiment up to the coating method of the above-mentioned embodiment.

FIG. 7 is a front sectional view showing an application head used in a method for applying a thermosetting adhesive which is another embodiment of the present invention.

FIG. 8 is a front sectional view showing an application head used in a method for applying a thermosetting adhesive, which is still another embodiment of the present invention.

FIG. 9 is a front sectional view showing an application head used in a method for applying a heat-effect adhesive which is still another embodiment of the present invention.

FIG. 10 is a front sectional view showing an application head used in a method for applying a heat-effect adhesive, which is still another embodiment of the present invention.

[Explanation of symbols]

 12 Syringe 16 Application Nozzle 20 Adhesive 32 Air Chamber 80 Air Chamber 82 Syringe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Manabu Mizuno 19 Chausan, Yamamachi, Chiryu-shi, Aichi Fuji Machinery Co., Ltd. (72) Inventor Seiichi Terui 19 Address Fuji Machine Manufacturing Co., Ltd. (56) Reference JP 62-269395 (JP, A) Actual 62-190669 (JP, U) Actual 63-13278 (JP, U)

Claims (1)

(57) [Claims] 1. A coating step of discharging a thermosetting adhesive contained in a syringe from a nozzle by supplying a compressed gas to coat an object to be coated, and an exhaust for discharging the compressed gas supplied to the syringe. A method of applying a thermosetting adhesive, comprising a step of scavenging the gas remaining in the syringe with fresh air after the evacuation step.